Understanding Mechanical Activation of Chemical Reactions on Surfaces

先进材料的开发对于制造新产品以及经济和国家安全至关重要，其应用遍及多个工业部门，包括国防，能源，交通，航空航天和医疗保健。由这些新材料制成的机器将需要润滑剂来降低摩擦并减轻针对特定材料定制的磨损。新的润滑剂通常是通过反复试验设计的，这可能是一个漫长而不确定的过程。不幸的是，很少被理解的基本化学过程发生在滑动界面，导致形成的摩擦和/或磨损减少膜。这项工作的目标是利用一系列表面分析工具和新的理论方法，以获得对作用于表面的力影响化学的方式的基本见解，从而为先进材料设计新的润滑剂。这项工作也将大大提高我们对机械诱导过程的理解。机械化学合成已广泛用于有机化学中，以在无溶剂环境中制备分子，合成药物和新型无机材料，并且机械过程在生物学中无处不在。这项工作将为机械化学反应提供基本的分子尺度见解，这将对美国经济产生积极影响。在实验和理论方法方面获得经验的学生将为他们提供化学、物理和材料科学方面的广泛的多学科教育，并将专门针对女性和少数民族的研究。该项目将研究二烷基二硫化物和羧酸等小分子对铜的气相润滑作用。本文将在真空度为100 ℃的条件下研究润滑膜形成的反应途径，以确定基元级反应。在准静态条件下进行的密度泛函理论计算得到的活化能与实验测量的机械化学反应动力学压缩下使用原子力显微镜针尖。 因此，本研究利用在以前的研究中开发的实验和理论工具箱来解决两个基本问题：1。了解和预测组合法向和侧向应力对表面摩擦化学反应速率的影响。了解结合到基底和移动的对立面影响摩擦化学反应的方式。这个奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The development of advanced materials is essential for manufacturing new products and for economic and national security, with applications across multiple industrial sectors including defense, energy, transportation, aerospace, and healthcare. Machines made from these new materials will require lubricants to lower friction and mitigate wear that are tailored to the specific material. New lubricants are often designed by trial and error, which can be a long and uncertain process. Unfortunately, little is understood of the fundamental chemical processes occurring at a sliding interface that lead to formation of friction and/or wear reducing films. The goal of this work is to exploit an array of surface analytical tools and novel theoretical approaches to obtain fundamental insights into the way that forces acting on the surface influence the chemistry to take the guesswork out of designing new lubricants for advanced materials. The work will also significantly improve our understanding of mechanically induced processes in general. Mechanochemical syntheses have been widely used in organic chemistry to make molecules in a solvent-free environment, to synthesize pharmaceuticals and novel inorganic materials, and mechanical processes are ubiquitous in biology. This work will provide fundamental molecular-scale insights into mechanochemical reactions that will positively impact the United States’ economy. Students gaining experience in the experimental and theoretical methods will provide them with a broad multidisciplinary education in chemistry, physics and materials science and will be specifically targeted at including females and minorities in the research.The project will investigate the gas-phase lubrication of copper by small molecules such as dialkyl disulfides and carboxylic acids. The reaction pathway for the formation of lubricating films will be studied in ultrahigh vacuum to identify the elementary step reactions. Density functional theory calculations carried out under quasistatic conditions have yielded activation energies in good agreement with experimental measurements of mechanochemical reaction kinetics under compression using an atomic force microscope tip. Thus, the research exploits this experimental and theoretical toolbox developed during previous studies to addresses two fundamental issues: 1. To understand and predict the effect of combined normal and lateral stresses on the rates of tribochemical reactions on surfaces and 2. To understand the way in which binding to the substrate and the moving counterface influences tribochemical reactivity. The project will involve outreach to underrepresented undergraduates as well as outreach to Latin America and West Africa.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.